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讨论了16QAM调制时应用不同类型和参数的滤波器对系统性能的影响.针对16QAM的特点,采用了存储波形累加求和法来代替一般的滤波成形,提高了调制速度.并利用其相位对称的特点将波形存储表压缩为原容量的1/4,有效地节约了存储空间. 相似文献
63.
Voltage contrast (VC) has been a powerful tool for the failure analysis of integrated circuits and multichip module. As the packing density of printed circuit board (PCB) is increasing, conventional failure analysis methods to detect open or short circuit in PCBs are no longer adequate, and voltage contrast method could be a method for this purpose. However, unlike the cases of integrated circuits and multichip module, there are many areas in PCB that will produce serious charging effect when examine under the scanning electron microscope. One of the areas is the presence of solder mask on PCB.This work examines the feasibility of using voltage contrast for PCB failure analysis. Specially designed PCB is used for experimentation, and it is found that positive bias on one track and zero bias on another copper track provide a better image contrast as compared to negative and zero biases on the tracks. Also, the variation of the image contrast with different spacing between inter copper tracks has studied. It is found that the variation depends on the presence of solder mask and its location. The variation can be very different for negative bias case as compared to the positive bias case.Finite element analysis is also performed to explain the experimental observations. All the observations can be well explained by the charging effect of the solder masks. The charging effect of solder mask is indeed very significant in affecting the image contrast, and it could reduce the contrast to almost zero in some cases. 相似文献
64.
Leong Che Kan; Hau Kit Tai; Cheng Pui Wan; Tan Li Hai 《Canadian Metallurgical Quarterly》2005,97(4):591
In a 2-wave study of a cohort of 108 Chinese students (10- to 11-year-olds) learning English as a second language, the authors examined the relative effects of three Time 1 latent constructs-- orthographic knowledge, phonological sensitivity, and word identification (reading and spelling of regular and exception words)--on the respective Time 2 performance. The authors posited autoregressive effects, in which Time 1 constructs affected their matching Time 2 performance (e.g., Time 1 orthographic knowledge on Time 2 orthographic knowledge), as well as reciprocal cross-domain effects (e.g., orthographic knowledge on word identification and vice versa). The model converged to a proper solution with reasonably good fit. The results suggest (a) strong stability in the children's word identification and phonological sensitivity, (b) substantial effects of word identification on subsequent orthographic knowledge and phonological sensitivity, particularly the former; and (c) greater variations in individuals' growth of orthographic knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
根据铝型材氧化着色电泳自动生产线的布局结构及其PLC控制网络系统的特点,应用组态软件RSView32及嵌入式VBA开发该生产线的自动监控系统。介绍了监控工作站与PLC站点的数据通信接口及实现方法。应用基于事件驱动的动态调度方法实现行车的动态调度与决策,并给出了主要程序模块的工作流程图。 相似文献
66.
构造高可靠性的电子商务系统,不能单从硬件或软件的角度考虑,而必须从硬件和软件的体系结构出发,充分利用它们的特点,编写适合于这种体系结构的应用程序。只有这样,才能提高系统的综合性能。本文在分析机群技术和N层软件体系结构的基础上,介绍了基于机群和N层体系结构的电子商务系统构建技术和方法。 相似文献
67.
适合铝丝键合后热老化要求的金导体浆料 总被引:1,自引:2,他引:1
研究了一种适合铝丝键合后热老化要求的金导体浆料,性能达到使用要求。在金浆中添加了少量合金元素,并选用混合型粘结剂。对金导体铝丝焊后热老化失效机理以及添加合金元素的作用,进行了讨论 相似文献
68.
Tsai FC Tai LA Wang YJ Xiao JL Hsu TH Yang CS Lee CH 《Microscopy research and technique》2011,74(6):531-538
Gold nanoparticles (AuNPs) confined in liposomes of diameters around 200 nm produce strong scattering signal owing to surface plasmon resonance, and therefore bright-field optical tracking of the AuNP-encapsulating liposomes can be conducted in living cells. Using an optical profiling technique called noninterferometric wide-field optical profilometry and a bright-field tracking algorithm, the polynomial-fit Gaussian weight method, we analyze three-dimensional (3D) motion of such liposomes in living fibroblasts. The positioning accuracy in three dimensions is nearly 20 nm. We tag the liposome membranes with fibroblast growth factor-1 and reveal the intracellular transportation processes toward or away from the nucleus. On the basis of a temporal analysis of the intracellular 3D trajectories of AuNP-encapsulating liposomes, we identify directed and diffusive motions in the transportation processes. 相似文献
69.
Dodd Alyson L.; Mansell Warren; Morrison Anthony P.; Tai Sara 《Canadian Metallurgical Quarterly》2011,23(3):635
The Hypomanic Attitudes and Positive Predictions Inventory (HAPPI; W. Mansell, 2006) was developed to assess multiple, extreme, self-relevant appraisals of internal states. The present study aimed to validate the HAPPI in a clinical sample. Participants (N = 50) with a diagnosis of bipolar disorder (confirmed by a structured clinical interview) completed a series of questionnaires pertaining to clinical factors, reward motivation, cognitive style, symptoms, and functioning at baseline, in addition to the HAPPI. Over the following 4 weeks, participants were asked to complete self-report measures of symptoms (activation, perceived conflict, depression, and well-being), as well as work and social functioning, twice weekly. The authors hypothesized that the HAPPI would be associated with prospective bipolar symptoms and functioning, when controlling for baseline symptoms and potentially confounding measures. The HAPPI was positively, independently associated with activation and conflict after 4 weeks. Furthermore, individual HAPPI factors were associated with activation, conflict, and depression. The results provided preliminary support for the predictive validity of the HAPPI in a clinical sample. The HAPPI could be used in the future as a tool in cognitive behavioral therapy for bipolar disorder to identify problematic beliefs and guide formulation. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
70.